Gearshift arrangement for a motor vehicle change-speed gear

ABSTRACT

A gearshift arrangement for a motor vehicle change-speed gear, primarily for use with a transversely mounted engine, includes a manual gearshift lever articulated to a selector shaft that is mounted for selective longitudinal displacement and rotary movement. Shift forks are effecting movement of slidable shift coupling sleeves or a slidable pinion are formed as angled pivotal shift forks having free lever ends which, during a gearshift, are engaged directly by selector fingers that effectively form part of the selector shaft.

[ 1 May 8, 1973 United States Patent [191 Renk m n m a m n m n M K .m .7n m 1 F m m a m m u 7 E M W 0 a a .m a r 3 P.

Rolf Renk, Russelsheim, Main,'Ger many Attorney- W. E. Finken et al.

[73] Assignee: General Motors Corporation, a

A gearshift arrangement for a motor vehicle change- Detroit, Mich.

[22] Filed: Nov. 24, 1971 speed gear, primarily for use with atransversely [21] Appl. No.: 201,796 mounted engine, includes a manualgearshift lever articulated to a selector shaft that is mounted forselec- [30] Foreign Application Priority Data tive longitudinaldisplacement and rotary movement.

Shift forks are effecting movement of slidable shift coupling sleeves ora slidable pinion are formed as an- Dec. 19, 1970Germany.....................P 20 62 691.9

Y gled pivotal shift forks having free lever ends which, 5%duringagmm,wageddirectlybysemfing that effectively q p of the Selectorshaft- [58] Field of Search....................74/473 R, 475, 476,

8 cm; seawater [56] References Cited 7 UNITED STATES PATENTS 3,264,8938/1966 Stott et al. ....74/477 PATENIED 81975 3,731,554

SHEET 1 OF 4 Fig. 1

lnvenlor A tlorney PATENTED J 8|9T3 I SHEET 2 BF 4 PATENTED 8% 3,731,554

SHEET30F4 I nvenlor 1% 15 6221 B? amzlim/ A Horney PATENTED MAY 81975SHEET 4 0F 4 GEARSHIFT ARRANGEMENT FOR A MOTOR VEHICLE CHANGE-SPEED GEARThe invention relates to gearshift arrangements for motor vehiclechange-speed gears, primarily for motor vehicles having an engineextending transversely to the direction of vehicle travel, with agearshift lever articulated to a shaft which is mounted so as to beselectively longitudinally displaceable and rotatable, for the purposeof selecting and actuating one of a plurality of gearshift forks.

Such gearshift arrangements, utilized generally in conjunction with anormal, lengthwise arrangement of the engine, usually involve the use ofseveral longitudinally displaceable shift fork rods, on each of which ashift fork is mounted for selective engagement of two adjacent gearratios. For actuation of such gearshift arrangements, first of all oneof the shift fork rods is selected, whereupon the selected shift forkrod is displaced in a longitudinal direction, to cause an associatedshift fork to move a synchronizing clutch (coupling sleeve) or a slidingpinion, for engagement of the desired gear ratio.

In such shift arrangements, the gearshift lever may by articulated bymeans of a double joint to the shaft (selector shaft) which is mountedso as to be selectively longitudinally displaceable and rotatable.During the selecting operation, a selector finger or similar projectionon the shaft is brought into alignment or engagement with a recess inone of the shift fork rods, and then, by longitudinal displacement ofthe shaft, and consequently of the associated shift fork rod, thedesired gear ratio is engaged. In this gearbox operation, the pattern ofmovement of the gearshift lever (for example a floor-mounted shiftlever) is determined by an H-shaped shift gate. The H-shaped gear-changepattern is used in practically all well-known types of automobilesutilizing a manual shift, and will therefore be familiar to all drivers;

With the introduction of transversely mounted engines with theassociated gearbox parallel to the engine, it is desirable to be able toretain the proven H-shaped gearshift pattern unchanged, but previousattempts to do this have involved a complicated releasable connec tionbetween shift fork rod and selector shaft, because the transversearrangement of the gearbox made it necessary for the gearshift forces tobe turned through problem is obtainable only by abandoning theconventional idea of arranging the shift forks on axially displaceableshift fork rods, and instead utilizing shift forks which are shaped andmounted as angled pivotal forks, and have respective free lever endswhich, during the shift, directly engage the shaft that is actuated bythe manual gearshift lever.

Thereby, separate shift fork rods become unnecessary, as do costlyconnecting elements between the selector shaft and the shift forks,since the conversion of the longitudinally directed gear-change effortinto an essentially transverse movement is now effected by the angledpivotal shift forks themselves. Accordingly, the present gearshiftarrangement is able to operate directly, with an easy action and largelywithout play, and utilizes only a small number of transmission elements,such that it involves relatively low production costs and allows a verycompact gearshift layout.

The present arrangement is not limited in application to gearboxes whichextend at right angles to the direction of vehicle travel, but canreadily be utilized with gearboxes which extend transversely at anyangle to the longitudinal axis of the vehicle, it being merely necessaryto adapt the angle of the pivotal shift forks to this angle. For agearbox arranged at right angles to the direction of vehicle travel, itis considered desirable for the pivotal shift forks to be right-angledand to be pivotally mounted at the vertex of the right angle.

By appropriate choice of the lever arm lengths of the pivotal shiftforks, it is also possible to step up or step down the gearshift forcesor movements. For the most direct transmission of the gearshift forces,the leverarm length of the shift fork should be approximately the sameas the effective length of the free lever portion co-operating with theselector shaft.

The pivotal shift forks may be actuated by selector fingers whichproject in a generally radially direction from the end portion of theselector shaft and are selec- V tively engageable with a respectivegroove in the free an angle of 90. Further, there may be an undesirableincrease in the amount of possible play in the mechanism, and a tendencyto engage more than one gear ratio at a time. Additionally, suchattempts-tend to involve the use of more than one (generally three, forfour forward ratios and reverse) of the shift fork rods. For suchreasons it tends to be difficult to achieve a precise, light-action andplay-free transmission of the gear-changing forces.

The present invention is concerned with the problem ofovercoming theabove defects in the known gearshift arrangements for gearboxesextending transversely, in other words the problem of achieving a shiftarrangement of the kind referred to which will require only fewconnecting elements from gearshift lever to shift fork and willtherefore make possible a direct and easy action in the transmission ofthe gear-change forces to the shiftcoupling sleeves in the gearbox. Theinvention is based on the concept that a satisfactory solution of thelever end of each of the pivotal shift forks. For a change-speed gearwith four forward ratios and a reverse, according to the invention, twoselector fingers at an angle to one another may be arranged at the endof the shaft, such that one selector finger co-operates with the twopivotal shift forks for first and second, and third and fourth, ratiosrespectively, whereas theother selector finger serves to engage thepivotal shift fork for the reverse ratio.

With the invention, it is also possible to avoid actuating two shiftcoupling dollars at the same time, without the complication ofadditional parts, by utilizing selector fingers of a thickness less thanthe distance between the shift fork control grooves, such that theselector fingers cannot be in engagement with two pivotal shift forkssimultaneously.

Furthermore, in order to prevent a shift movement taking place when,during theselection movement, a selector finger has taken up a positionbetween the control grooves of two pivotal shift forks, or in order toprevent selection movement when a gear ratio is already engaged, alocking device may be utilized, for example a gearshift gate which isarranged for example above the rod and is engaged by a pin-or similarprojection firmly connected to the rod.

For the reverse ratio there may be an additional locking device. Forexample, for an arrangement in which the selector shaft is actuated by auniversally mounted gearshift lever having a peg-shaped extensionunderneath its universal mounting, the additional locking device for thereverse ratio may comprise a stop that is disposed at the bottom of thebearing housing for the shaft and can only be over-ridden by lifting thegearshift lever.

In order to prevent jump-out of the gears when engaged, the pivotalshift forks may have a snap-in detent catch device having a position foreach gear ratio and possibly also a neutral position. Thus the pivotalshift fork for the first and second gear ratios, and the pivotal shiftfork for the third and fourth ratios, may each have three snap-inpositions, whereas a detent catch device may be used for the reverseratio which gives only two positions. A catch device which offers theadvantages of simplicity and certainty of operation is one in which thepivotal shift forks include a lever extension beyond their pivot axes,with the free end of each extension widened into hammer shape and havingdetent grooves for yieldable engagement by a spring-urged ball.

In the drawings:

FIG. 1 is a fragmentary schematic plan showing the front portion of amotor vehicle with a transversely mounted engine;

FIG. 2 is a fragmentary longitudinal vertical section through agearshift arrangement that is shown generally in FIG. 1, looking towardsa right-hand pivotal shift fork;

FIG. 3 is a view in a forward direction showing the main parts of thegearshift arrangement of FIGS. 1 and FIG. 4 is an underneath view of thegearshift arrangement of FIGS. 1 to 3, but with the pivotal shift forkfor the first and second gear ratios omitted for clarity; and

FIG. 5 is a fragmentary section on the line V--V of FIG. 2, in thedirection of the arrows.

lnthe general view shown in FIG. 1, the front portion of an automobileis shown as including a pair of front wheels 11 and 12, a steering wheeland steering column 13 and 14, a steering gear 15, a track rod 16,steering arms 17 and 18, an engine 19 mounted transversely to thedirection of vehicle travel 20, a cooling fan 21, and a change-speedgearbox 22 arranged parallel to the engine 19, and therefore likewisetransversely to the direction of vehicle travel 20. For driving thefront wheels, half-shafts 23 and 24 extend from the gearbox 22, withrespective rubber sealing gaiters 25 and 26 to exclude dust and moistureand prevent the escape of lubricant.

FIG. 1 also shows two shift coupling sleeves 27 and 28 which form partof a gearshift arrangement and are axially displaceable on thetransmission mainshaft 29 in the direction of the arrows 30.Displacement of the coupling sleeves 27 and 28 either actuates asynchronizing clutch or moves a sliding pinion, in a manner known perse, thereby engaging the desired gear ratio, the coupling sleeve 27serving for engaging the third (right-hand position) and fourth(left-hand position) gear ratios whereas the coupling sleeve 28 effectsengagement of the first (left-hand position) and second (right-handposition) ratios. Reverse ratio is engaged by the direct displacement ofa pinion 31 (FIG.

4) on a shaft 32 indicated in FIG. 1 as an interrupted line. Pinion 31has been omitted from FIG. 1 for clarity but will be seen in theenlarged view of FIG. 4, which will be further considered below ingreater detail. In the position illustrated in the drawings, the shiftcoupling sleeves 27 and 28 and the sliding pinion 31 are in the neutralposition.

As will be seen particularly from FIGS. 2, 3 and 4, acutation of theshift coupling sleeves 27 and 28 or of the sliding pinion 31 is broughtabout by shift forks 33, 34 or 35 respectively, which are formed asangled pivotal shift forks, having an angle of 90 between first andsecond lever portions of each fork, and are mounted on pivot pins 48 and49 respectively which are press-fitted into the housing of the gearbox22 (FIG. 2). The pivot pin 49 forms a mounting for both the pivotalshift forks 34 and 35. The respective pivot axes are designated 36, 37and 38.

A forwardly directed lever portion 39 or 40 or 41 (first lever portion)of each pivotal shift fork is bifurcated and straddles a shift couplingsleeve 27 or 28 or the sliding pinion 31, as the case may be, whereas asecond lever portion 42 or 43 or 44 of each shift fork is arranged atright angles to the first lever portion of the respective shift fork andhas a shift control groove 45, 46, 47 respectively at its free end. Thecontrol grooves 45 and 46 are arranged for selective co-operation with aselector finger 50, and the control groove 47 is arranged for selectiveco-operation with a separate selector finger 51. The selector fingers 50and 51 extend from a common boss portion 52 formed by a hub fixed to arotatable and axially displaceable selector shaft 53, and thuseffectively form part of the shaft. A pin 54 extends through the bossportion 52 and shaft 53, and has an upwardly projecting end portionwhich co-operates with a gate 55 that is screwed (at position 57 shownin FIG. 2) on to a front wall 56 of the gearbox 22, above the selectorshaft 53.

It is not strictly necessary to lock the non-actuated shift couplingsleeves 27 and 28 and sliding pinion 31,

because the thickness of the selector fingers 50 and 51 is less than thedistance (a in FIG. 3) between the shift control grooves 45 and 46 inthe second lever portions 42 and 43, such that in an intermediateposition of the selector fingers it is not possible to engage twopivotal shift forks simultaneously. However, to ensure that no shiftmovement at all can take place when the selector fingers 50 and 51 arein a position between the lever portions 42 and 43 of the pivotal shiftforks 33 and 34, and further to prevent a selecting movement fromoccurring when a gear ratio is engaged, the gate 55 above the shaft 53is provided with a recess for the pin 54, this recess corresponding tothe shift movement. The recess of the gate 55' has five channels 58-62,namely a channel 58 for the first ratio, a channel 59 for the second, achannel 60 for the third, 21 channel 61 for the fourth and a channel 62for the reverse ratio, as is best seen in F IG. 4, a cross-channel 63being provided for selection of the required gear-ratio plane 58/59, or60/61, or 62. In the shift position shown in FIGS. 1 and 4, the pin 54is positioned within the selection cross-channel 63, in the gear-ratioplane 58/59. Therefore, in this position, by appropriate displacement ofthe shaft 53 in an axial direction (corresponding to the arrow 64),engagement of the first or second forward ratio is possible.

As will be seen particularly from FIGS. 1 and 2, the displacementmovement of the shaft 53, and also its rotary movement required for theselection, is brought about in a manner known per se by means of afloormounted gearshift lever 65 having a universal mounting with a pivotcenter 66 in the vehicle body. As is shown in FIG. 2, the lower end 67of the gearshift lever is pegshaped, with a part-spherical head 68forming a pivotal connection to a cranked lever 69 that is mounted bymeans ofa hollow boss 70 and securing pin 71 in a rotationally fastmanner on the rear end portion of the selector shaft 53. The mainmounting for the rotatable and longitudinally .displaceable selectorshaft is the front wall 56 of the gearbox, at bearing surfaces 72 and73, with a seal 74 to prevent the escape of oil from the gearbox.

The mode of operation of the shift arrangement is, in summary asfollows:

Movement of the manual gearshift lever 65 in a direction transverse tothe direction of vehicle travel imparts rotary movement to the selectorshaft 53, such that one of the shift fingers 50 and 51 is aligned withor engages one of the shift control grooves 45-47 in the pivotal shiftforks 33-35, thereby selecting the desired gear-ratio plane. Before thegear-ratio plane 62 for reverse can be selected, an additional blockingdevice has to be overcome, namely stop 76 (FIG. 2) which is providedwith a longitudinal groove 75 and is located below the gearshift leverpeg 67, such that this reverse blocker can be over-ridden by lifting thegearshift lever 65. Thereupon, following this selection of the desiredgear-ratio plane, the manual gearshift lever 65 is moved in thedirection of vehicle travel, to produce longitudinal displacement of theselector shaft 53 for engagement of the required gear ratio. By adirect, easy and substantially play-free action, the longitudinalmovement of the selector shaft 53 is converted by the abovedescribedright-angled pivotal shift forks 3335 into transverse movement of theshift coupling sleeves 27, 28 or of the sliding pinion 31. As a matterof geometry, it will be observed that the ends of the pivotal shiftforks 33 and 34 which engage the shift coupling sleeves execute acircular movement, whereas-the movement of the shift coupling sleeves 27and 28 must be rectilinear. i

In order to prevent jump-out from the engaged ratios, or undesired ratioengagement from the neutral position, detent devices are provided forthe individual shift positions. For this purpose, as best seen in FIGS.2 and 4, the pivotal shift forks 33, 34, 35 are extended beyond theirpivot axis, to form lever extensions 79, 80, 8] containing detentgrooves 82, 83, 84 and 85, 86 in their respective hammer-shaped endportions. In the respective ratio positions, the detent grooves areengaged by spring-loaded detent balls 87. 88 and 89, the compressionsprings (such as 90 and 91) which springload these balls 87, 88, 89being supported in sleeves (such as 92 and 93) which are secured in thefront wall 56 of the gearbox 22.

l. Gearshift arrangement for a motor vehicle changespeed gear,comprising a housing, a selector shaft movably mounted within saidhousing, a manually operable gearshift lever, means for convertingmovement of the gearshift lever in a first plane into rotary movement ofthe selector shaft and for converting movement of the gearshift lever ina second plane into longitudinal displacement of the selector shaft,selector means disposed within said housing and fixed to said selectorshaft so as effectively to form a part thereof, and at least one angledpivotal shift fork disposed within said housing, said shift forkcomprising a first lever portion which is bifurcated for co-operationwith a respective gear coupling member, and said shift fork alsocomprising a second lever portion which is disposed at an angle to saidfirst lever portion and includes a free lever end that is shaped andarranged to be engaged directly by said selector means during agearshift.

2. Gearshift arrangement for a change-speed gear arranged in a motorvehicle in a direction at right angles to the direction of vehicletravel, comprising a selector shaft extending in the direction ofvehicle travel, means forming a movable mounting for said selectorshaft, means operable to produce selective rotary movement andlongitudinal displacement of said selector shaft,

selector means projecting in a generally radial direction from saidselector shaft and movable therewith, first and second shift forks eachcomprising a first lever portion that is bifurcated for co-operationwith a respective movable coupling member of said change-speed gear,each said shift fork also comprising, at right angles to said firstlever portion, a second lever portion having a free end that is shapedand arranged to be engaged directly by said selector means during agearshift, and spaced first and second vertically extending pivot pinsforming pivot mountings for the respective shift forks at the junctionof the first and second lever portions thereof, such that longitudinaldisplacement of said selector shaft causes a selected one of saidselector forks to pivot about its pivot pin to thereby effect movementof the associated coupling member of said change-speed gear in adirection at right angles to the direction of vehicle travel.

3. Gearshift arrangement according to claim 2, in

which said first and second lever portions of a shift fork as aforesaidare of substantially equal effective lengths.

4. Gearshift arrangement according to claim 2, in which said selectormeans projecting from said selector shaft comprises a finger that isarranged atone end of said shaft for selective co-operatioii with agroove formed in the. free end of the second lever portion of each ofsaid shift forks.

5. Gearshift arrangement for effecting selective movement of couplingmembers of a motor vehicle change-speed gear, comprising: a selectorshaft extending in the direction of vehicle travel; means forming amovable mounting for said selector shaft; means operable to produceselective rotary movement and longitudinal displacement of said selectorshaft; first and second selector fingers projecting in generally radialdirections from an end portion of said selector shaft and movabletherewith; first, second and third shift forks each comprising a firstlever portion that is bifurcated for co-operation with a respective oneof said coupling members, and also comprising, generally at right anglesto said first lever portion, a second lever portion having a grooveformed in the free end thereof; a first vertically extending pivot pinforming a pivot mounting for the first shift fork at the junction of thefirst and second lever portions thereof; a second vertically extendingpivot pin spaced from said first pivot pin and forming a pivot mountingfor both said second and said third shift forks at the junctions of thefirst and second lever portions of said shift forks; in an arrangementin which said first selector finger is selectively cooperable with saidgrooves in the free ends of the second lever portions of said first andsecond shift forks, and said second selector finger is selectivelycooperable with the groove in the free end of the second lever portionof said third shift fork, such that rotary movement of said selectorshaft brings one of said selector fingers into co-operating relationshipwith the groove in the free end of the second lever portion of aselected one of said shift forks, whereupon longitudinal displacement ofsaid selector shaft causes said selected shift fork to pivot about itspivot pin to thereby effect movement of the associated coupling memberof said change-speed gear in a direction transverse to the direction ofvehicle travel.

' 6. Gearshift arrangement according to claim 5, in which said firstselector finger has a width less than the distance between the free endsof the second lever portions of said first and second shift fork in theregion of said grooves therein.

7. Gearshift arrangement according to claim 6, in which said shift forksare formed with respective lever extensions beyond their respectivepivot pins, and spring-loaded detent balls are arranged for yieldableengagement in detend grooves in widened end portions of said leverextensions, for snap-in retention of said shift forks in position forthe particular gear ratio engaged, said first and second shift forksadditionally having an intermediate detent groove for establishing aneutral position.

8. Gearshift arrangement according to claim 7, in which a pin projectsfrom said selector shaft into a fixedly mounted shift gate that isarranged to establish a gearshift pattern by means of a selector channelcommunicating with individual channels corresponding to the respectiveratio positions, said pin co-operating with said channels to prevent ashift movement if the selector fingers are disposed between the groovesof two shift forks, and to prevent selection movement occurring if agear ratio is engaged.

1. Gearshift arrangement for a motor vehicle change-speed gear,comprising a housing, a selector shaft movably mounted within saidhousing, a manually operable gearshift lever, means for convertingmovement of the gearshift lever in a first plane into rotary movement ofthe selector shaft and for converting movement of the gearshift lever ina second plane into longitudinal displacement of the selector shaft,selector means disposed within said housing and fixed to said selectorshaft so as effectively to form a part thereof, and at least one angledpivotal shift fork disposed within said housing, said shift forkcomprising a first lever portion which is bifurcated for cooperationwith a respective gear coupling member, and said shift fork alsocomprising a second lever portion which is disposed at an angle to saidfirst lever portion and includes a free lever end that is shaped andarranged to be engaged directly by said selector means during agearshift.
 2. Gearshift arrangement for a change-speed gear arranged ina motor vehicle in a direction at right angles to the direction ofvehicle travel, comprising a selector shaft extending in the directionof vehicle travel, means forming a movable mounting for said selectorshaft, means operable to produce selective rotary movement andlongitudinal displacement of said selector shaft, selector meansprojecting in a generally radial direction from said selector shaft andmovable therewith, first and second shift forks each comprising a firstlever portion that is bifurcated for co-operation with a respectivemovable coupling member of said change-speed gear, each said shift forkalso comprising, at right angles to said first lever portion, a secondlever portion having a free end that is shaped and arranged to beengaged directly by said selector means during a gearshift, and spacedfirst and second vertically extending pivot pins forming pivot mountingsfor the respective shift forks at the junction of the first and secondlever portions thereof, such that longitudinal displacement of saidselector shaft causes a selected one of said selector forks to pivotabout its pivot pin to thereby effect movement of the associatedcoupling member of said change-speed gear in a direction at right anglesto the direction of vehicle travel.
 3. Gearshift arrangement accordingto claim 2, in which sAid first and second lever portions of a shiftfork as aforesaid are of substantially equal effective lengths. 4.Gearshift arrangement according to claim 2, in which said selector meansprojecting from said selector shaft comprises a finger that is arrangedat one end of said shaft for selective co-operation with a groove formedin the free end of the second lever portion of each of said shift forks.5. Gearshift arrangement for effecting selective movement of couplingmembers of a motor vehicle change-speed gear, comprising: a selectorshaft extending in the direction of vehicle travel; means forming amovable mounting for said selector shaft; means operable to produceselective rotary movement and longitudinal displacement of said selectorshaft; first and second selector fingers projecting in generally radialdirections from an end portion of said selector shaft and movabletherewith; first, second and third shift forks each comprising a firstlever portion that is bifurcated for co-operation with a respective oneof said coupling members, and also comprising, generally at right anglesto said first lever portion, a second lever portion having a grooveformed in the free end thereof; a first vertically extending pivot pinforming a pivot mounting for the first shift fork at the junction of thefirst and second lever portions thereof; a second vertically extendingpivot pin spaced from said first pivot pin and forming a pivot mountingfor both said second and said third shift forks at the junctions of thefirst and second lever portions of said shift forks; in an arrangementin which said first selector finger is selectively co-operable with saidgrooves in the free ends of the second lever portions of said first andsecond shift forks, and said second selector finger is selectivelyco-operable with the groove in the free end of the second lever portionof said third shift fork, such that rotary movement of said selectorshaft brings one of said selector fingers into co-operating relationshipwith the groove in the free end of the second lever portion of aselected one of said shift forks, whereupon longitudinal displacement ofsaid selector shaft causes said selected shift fork to pivot about itspivot pin to thereby effect movement of the associated coupling memberof said change-speed gear in a direction transverse to the direction ofvehicle travel.
 6. Gearshift arrangement according to claim 5, in whichsaid first selector finger has a width less than the distance betweenthe free ends of the second lever portions of said first and secondshift fork in the region of said grooves therein.
 7. Gearshiftarrangement according to claim 6, in which said shift forks are formedwith respective lever extensions beyond their respective pivot pins, andspring-loaded detent balls are arranged for yieldable engagement indetend grooves in widened end portions of said lever extensions, forsnap-in retention of said shift forks in position for the particulargear ratio engaged, said first and second shift forks additionallyhaving an intermediate detent groove for establishing a neutralposition.
 8. Gearshift arrangement according to claim 7, in which a pinprojects from said selector shaft into a fixedly mounted shift gate thatis arranged to establish a gearshift pattern by means of a selectorchannel communicating with individual channels corresponding to therespective ratio positions, said pin co-operating with said channels toprevent a shift movement if the selector fingers are disposed betweenthe grooves of two shift forks, and to prevent selection movementoccurring if a gear ratio is engaged.